# Copyright 2023 The HuggingFace Team. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

from dataclasses import dataclass
from math import ceil
from typing import Callable, List, Optional, Union

import numpy as np
import torch
from transformers import CLIPTextModel, CLIPTokenizer

from ...schedulers import DDPMWuerstchenScheduler
from ...utils import (
    BaseOutput,
    is_accelerate_available,
    is_accelerate_version,
    logging,
    replace_example_docstring,
)
from ...utils.torch_utils import randn_tensor
from ..pipeline_utils import DiffusionPipeline
from .modeling_wuerstchen_prior import WuerstchenPrior


logger = logging.get_logger(__name__)  # pylint: disable=invalid-name

DEFAULT_STAGE_C_TIMESTEPS = list(np.linspace(1.0, 2 / 3, 20)) + list(np.linspace(2 / 3, 0.0, 11))[1:]

EXAMPLE_DOC_STRING = """
    Examples:
        ```py
        >>> import torch
        >>> from diffusers import WuerstchenPriorPipeline

        >>> prior_pipe = WuerstchenPriorPipeline.from_pretrained(
        ...     "warp-ai/wuerstchen-prior", torch_dtype=torch.float16
        ... ).to("cuda")

        >>> prompt = "an image of a shiba inu, donning a spacesuit and helmet"
        >>> prior_output = pipe(prompt)
        ```
"""


@dataclass
class WuerstchenPriorPipelineOutput(BaseOutput):
    """
    Output class for WuerstchenPriorPipeline.

    Args:
        image_embeddings (`torch.FloatTensor` or `np.ndarray`)
            Prior image embeddings for text prompt

    """

    image_embeddings: Union[torch.FloatTensor, np.ndarray]


class WuerstchenPriorPipeline(DiffusionPipeline):
    """
    Pipeline for generating image prior for Wuerstchen.

    This model inherits from [`DiffusionPipeline`]. Check the superclass documentation for the generic methods the
    library implements for all the pipelines (such as downloading or saving, running on a particular device, etc.)

    Args:
        prior ([`Prior`]):
            The canonical unCLIP prior to approximate the image embedding from the text embedding.
        text_encoder ([`CLIPTextModelWithProjection`]):
            Frozen text-encoder.
        tokenizer (`CLIPTokenizer`):
            Tokenizer of class
            [CLIPTokenizer](https://huggingface.co/docs/transformers/v4.21.0/en/model_doc/clip#transformers.CLIPTokenizer).
        scheduler ([`DDPMWuerstchenScheduler`]):
            A scheduler to be used in combination with `prior` to generate image embedding.
    """

    def __init__(
        self,
        tokenizer: CLIPTokenizer,
        text_encoder: CLIPTextModel,
        prior: WuerstchenPrior,
        scheduler: DDPMWuerstchenScheduler,
        latent_mean: float = 42.0,
        latent_std: float = 1.0,
        resolution_multiple: float = 42.67,
    ) -> None:
        super().__init__()
        self.register_modules(
            tokenizer=tokenizer,
            text_encoder=text_encoder,
            prior=prior,
            scheduler=scheduler,
        )
        self.register_to_config(
            latent_mean=latent_mean, latent_std=latent_std, resolution_multiple=resolution_multiple
        )

    def enable_model_cpu_offload(self, gpu_id=0):
        r"""
        Offloads all models to CPU using accelerate, reducing memory usage with a low impact on performance. Compared
        to `enable_sequential_cpu_offload`, this method moves one whole model at a time to the GPU when its `forward`
        method is called, and the model remains in GPU until the next model runs. Memory savings are lower than with
        `enable_sequential_cpu_offload`, but performance is much better due to the iterative execution of the `unet`.
        """
        if is_accelerate_available() and is_accelerate_version(">=", "0.17.0.dev0"):
            from accelerate import cpu_offload_with_hook
        else:
            raise ImportError("`enable_model_cpu_offload` requires `accelerate v0.17.0` or higher.")

        device = torch.device(f"cuda:{gpu_id}")

        if self.device.type != "cpu":
            self.to("cpu", silence_dtype_warnings=True)
            torch.cuda.empty_cache()  # otherwise we don't see the memory savings (but they probably exist)

        hook = None
        for cpu_offloaded_model in [self.text_encoder]:
            _, hook = cpu_offload_with_hook(cpu_offloaded_model, device, prev_module_hook=hook)

        # We'll offload the last model manually.
        self.prior_hook = hook

        _, hook = cpu_offload_with_hook(self.prior, device, prev_module_hook=self.prior_hook)

        self.final_offload_hook = hook

    # Copied from diffusers.pipelines.unclip.pipeline_unclip.UnCLIPPipeline.prepare_latents
    def prepare_latents(self, shape, dtype, device, generator, latents, scheduler):
        if latents is None:
            latents = randn_tensor(shape, generator=generator, device=device, dtype=dtype)
        else:
            if latents.shape != shape:
                raise ValueError(f"Unexpected latents shape, got {latents.shape}, expected {shape}")
            latents = latents.to(device)

        latents = latents * scheduler.init_noise_sigma
        return latents

    def encode_prompt(
        self,
        device,
        num_images_per_prompt,
        do_classifier_free_guidance,
        prompt=None,
        negative_prompt=None,
        prompt_embeds: Optional[torch.FloatTensor] = None,
        negative_prompt_embeds: Optional[torch.FloatTensor] = None,
    ):
        if prompt is not None and isinstance(prompt, str):
            batch_size = 1
        elif prompt is not None and isinstance(prompt, list):
            batch_size = len(prompt)
        else:
            batch_size = prompt_embeds.shape[0]

        if prompt_embeds is None:
            # get prompt text embeddings
            text_inputs = self.tokenizer(
                prompt,
                padding="max_length",
                max_length=self.tokenizer.model_max_length,
                truncation=True,
                return_tensors="pt",
            )
            text_input_ids = text_inputs.input_ids
            attention_mask = text_inputs.attention_mask

            untruncated_ids = self.tokenizer(prompt, padding="longest", return_tensors="pt").input_ids

            if untruncated_ids.shape[-1] >= text_input_ids.shape[-1] and not torch.equal(
                text_input_ids, untruncated_ids
            ):
                removed_text = self.tokenizer.batch_decode(
                    untruncated_ids[:, self.tokenizer.model_max_length - 1 : -1]
                )
                logger.warning(
                    "The following part of your input was truncated because CLIP can only handle sequences up to"
                    f" {self.tokenizer.model_max_length} tokens: {removed_text}"
                )
                text_input_ids = text_input_ids[:, : self.tokenizer.model_max_length]
                attention_mask = attention_mask[:, : self.tokenizer.model_max_length]

            text_encoder_output = self.text_encoder(
                text_input_ids.to(device), attention_mask=attention_mask.to(device)
            )
            prompt_embeds = text_encoder_output.last_hidden_state

        prompt_embeds = prompt_embeds.to(dtype=self.text_encoder.dtype, device=device)
        prompt_embeds = prompt_embeds.repeat_interleave(num_images_per_prompt, dim=0)

        if negative_prompt_embeds is None and do_classifier_free_guidance:
            uncond_tokens: List[str]
            if negative_prompt is None:
                uncond_tokens = [""] * batch_size
            elif type(prompt) is not type(negative_prompt):
                raise TypeError(
                    f"`negative_prompt` should be the same type to `prompt`, but got {type(negative_prompt)} !="
                    f" {type(prompt)}."
                )
            elif isinstance(negative_prompt, str):
                uncond_tokens = [negative_prompt]
            elif batch_size != len(negative_prompt):
                raise ValueError(
                    f"`negative_prompt`: {negative_prompt} has batch size {len(negative_prompt)}, but `prompt`:"
                    f" {prompt} has batch size {batch_size}. Please make sure that passed `negative_prompt` matches"
                    " the batch size of `prompt`."
                )
            else:
                uncond_tokens = negative_prompt

            uncond_input = self.tokenizer(
                uncond_tokens,
                padding="max_length",
                max_length=self.tokenizer.model_max_length,
                truncation=True,
                return_tensors="pt",
            )
            negative_prompt_embeds_text_encoder_output = self.text_encoder(
                uncond_input.input_ids.to(device), attention_mask=uncond_input.attention_mask.to(device)
            )

            negative_prompt_embeds = negative_prompt_embeds_text_encoder_output.last_hidden_state

        if do_classifier_free_guidance:
            # duplicate unconditional embeddings for each generation per prompt, using mps friendly method
            seq_len = negative_prompt_embeds.shape[1]
            negative_prompt_embeds = negative_prompt_embeds.to(dtype=self.text_encoder.dtype, device=device)
            negative_prompt_embeds = negative_prompt_embeds.repeat(1, num_images_per_prompt, 1)
            negative_prompt_embeds = negative_prompt_embeds.view(batch_size * num_images_per_prompt, seq_len, -1)
            # done duplicates

        return prompt_embeds, negative_prompt_embeds

    def check_inputs(
        self,
        prompt,
        negative_prompt,
        num_inference_steps,
        do_classifier_free_guidance,
        batch_size,
    ):
        if not isinstance(prompt, list):
            if isinstance(prompt, str):
                prompt = [prompt]
            else:
                raise TypeError(f"'prompt' must be of type 'list' or 'str', but got {type(prompt)}.")

        if do_classifier_free_guidance:
            if negative_prompt is not None and not isinstance(negative_prompt, list):
                if isinstance(negative_prompt, str):
                    negative_prompt = [negative_prompt]
                else:
                    raise TypeError(
                        f"'negative_prompt' must be of type 'list' or 'str', but got {type(negative_prompt)}."
                    )

        if not isinstance(num_inference_steps, int):
            raise TypeError(
                f"'num_inference_steps' must be of type 'int', but got {type(num_inference_steps)}\
                           In Case you want to provide explicit timesteps, please use the 'timesteps' argument."
            )

        batch_size = len(prompt) if isinstance(prompt, list) else 1

        return prompt, negative_prompt, num_inference_steps, batch_size

    @torch.no_grad()
    @replace_example_docstring(EXAMPLE_DOC_STRING)
    def __call__(
        self,
        prompt: Optional[Union[str, List[str]]] = None,
        height: int = 1024,
        width: int = 1024,
        num_inference_steps: int = 60,
        timesteps: List[float] = None,
        guidance_scale: float = 8.0,
        negative_prompt: Optional[Union[str, List[str]]] = None,
        prompt_embeds: Optional[torch.FloatTensor] = None,
        negative_prompt_embeds: Optional[torch.FloatTensor] = None,
        num_images_per_prompt: Optional[int] = 1,
        generator: Optional[Union[torch.Generator, List[torch.Generator]]] = None,
        latents: Optional[torch.FloatTensor] = None,
        output_type: Optional[str] = "pt",
        return_dict: bool = True,
        callback: Optional[Callable[[int, int, torch.FloatTensor], None]] = None,
        callback_steps: int = 1,
    ):
        """
        Function invoked when calling the pipeline for generation.

        Args:
            prompt (`str` or `List[str]`):
                The prompt or prompts to guide the image generation.
            height (`int`, *optional*, defaults to 512):
                The height in pixels of the generated image.
            width (`int`, *optional*, defaults to 512):
                The width in pixels of the generated image.
            num_inference_steps (`int`, *optional*, defaults to 30):
                The number of denoising steps. More denoising steps usually lead to a higher quality image at the
                expense of slower inference.
            timesteps (`List[int]`, *optional*):
                Custom timesteps to use for the denoising process. If not defined, equal spaced `num_inference_steps`
                timesteps are used. Must be in descending order.
            guidance_scale (`float`, *optional*, defaults to 4.0):
                Guidance scale as defined in [Classifier-Free Diffusion Guidance](https://arxiv.org/abs/2207.12598).
                `decoder_guidance_scale` is defined as `w` of equation 2. of [Imagen
                Paper](https://arxiv.org/pdf/2205.11487.pdf). Guidance scale is enabled by setting
                `decoder_guidance_scale > 1`. Higher guidance scale encourages to generate images that are closely
                linked to the text `prompt`, usually at the expense of lower image quality.
            negative_prompt (`str` or `List[str]`, *optional*):
                The prompt or prompts not to guide the image generation. Ignored when not using guidance (i.e., ignored
                if `decoder_guidance_scale` is less than `1`).
            prompt_embeds (`torch.FloatTensor`, *optional*):
                Pre-generated text embeddings. Can be used to easily tweak text inputs, *e.g.* prompt weighting. If not
                provided, text embeddings will be generated from `prompt` input argument.
            negative_prompt_embeds (`torch.FloatTensor`, *optional*):
                Pre-generated negative text embeddings. Can be used to easily tweak text inputs, *e.g.* prompt
                weighting. If not provided, negative_prompt_embeds will be generated from `negative_prompt` input
                argument.
            num_images_per_prompt (`int`, *optional*, defaults to 1):
                The number of images to generate per prompt.
            generator (`torch.Generator` or `List[torch.Generator]`, *optional*):
                One or a list of [torch generator(s)](https://pytorch.org/docs/stable/generated/torch.Generator.html)
                to make generation deterministic.
            latents (`torch.FloatTensor`, *optional*):
                Pre-generated noisy latents, sampled from a Gaussian distribution, to be used as inputs for image
                generation. Can be used to tweak the same generation with different prompts. If not provided, a latents
                tensor will ge generated by sampling using the supplied random `generator`.
            output_type (`str`, *optional*, defaults to `"pil"`):
                The output format of the generate image. Choose between: `"pil"` (`PIL.Image.Image`), `"np"`
                (`np.array`) or `"pt"` (`torch.Tensor`).
            return_dict (`bool`, *optional*, defaults to `True`):
                Whether or not to return a [`~pipelines.ImagePipelineOutput`] instead of a plain tuple.
            callback (`Callable`, *optional*):
                A function that will be called every `callback_steps` steps during inference. The function will be
                called with the following arguments: `callback(step: int, timestep: int, latents: torch.FloatTensor)`.
            callback_steps (`int`, *optional*, defaults to 1):
                The frequency at which the `callback` function will be called. If not specified, the callback will be
                called at every step.

        Examples:

        Returns:
            [`~pipelines.WuerstchenPriorPipelineOutput`] or `tuple` [`~pipelines.WuerstchenPriorPipelineOutput`] if
            `return_dict` is True, otherwise a `tuple`. When returning a tuple, the first element is a list with the
            generated image embeddings.
        """

        # 0. Define commonly used variables
        device = self._execution_device
        do_classifier_free_guidance = guidance_scale > 1.0
        batch_size = len(prompt) if isinstance(prompt, list) else 1

        # 1. Check inputs. Raise error if not correct
        prompt, negative_prompt, num_inference_steps, batch_size = self.check_inputs(
            prompt, negative_prompt, num_inference_steps, do_classifier_free_guidance, batch_size
        )

        # 2. Encode caption
        prompt_embeds, negative_prompt_embeds = self.encode_prompt(
            prompt=prompt,
            device=device,
            num_images_per_prompt=num_images_per_prompt,
            do_classifier_free_guidance=do_classifier_free_guidance,
            negative_prompt=negative_prompt,
            prompt_embeds=prompt_embeds,
            negative_prompt_embeds=negative_prompt_embeds,
        )

        # For classifier free guidance, we need to do two forward passes.
        # Here we concatenate the unconditional and text embeddings into a single batch
        # to avoid doing two forward passes
        text_encoder_hidden_states = (
            torch.cat([prompt_embeds, negative_prompt_embeds]) if negative_prompt_embeds is not None else prompt_embeds
        )

        # 3. Determine latent shape of image embeddings
        dtype = text_encoder_hidden_states.dtype
        latent_height = ceil(height / self.config.resolution_multiple)
        latent_width = ceil(width / self.config.resolution_multiple)
        num_channels = self.prior.config.c_in
        effnet_features_shape = (num_images_per_prompt * batch_size, num_channels, latent_height, latent_width)

        # 4. Prepare and set timesteps
        if timesteps is not None:
            self.scheduler.set_timesteps(timesteps=timesteps, device=device)
            timesteps = self.scheduler.timesteps
            num_inference_steps = len(timesteps)
        else:
            self.scheduler.set_timesteps(num_inference_steps, device=device)
            timesteps = self.scheduler.timesteps

        # 5. Prepare latents
        latents = self.prepare_latents(effnet_features_shape, dtype, device, generator, latents, self.scheduler)

        # 6. Run denoising loop
        for i, t in enumerate(self.progress_bar(timesteps[:-1])):
            ratio = t.expand(latents.size(0)).to(dtype)

            # 7. Denoise image embeddings
            predicted_image_embedding = self.prior(
                torch.cat([latents] * 2) if do_classifier_free_guidance else latents,
                r=torch.cat([ratio] * 2) if do_classifier_free_guidance else ratio,
                c=text_encoder_hidden_states,
            )

            # 8. Check for classifier free guidance and apply it
            if do_classifier_free_guidance:
                predicted_image_embedding_text, predicted_image_embedding_uncond = predicted_image_embedding.chunk(2)
                predicted_image_embedding = torch.lerp(
                    predicted_image_embedding_uncond, predicted_image_embedding_text, guidance_scale
                )

            # 9. Renoise latents to next timestep
            latents = self.scheduler.step(
                model_output=predicted_image_embedding,
                timestep=ratio,
                sample=latents,
                generator=generator,
            ).prev_sample

            if callback is not None and i % callback_steps == 0:
                callback(i, t, latents)

        # 10. Denormalize the latents
        latents = latents * self.config.latent_mean - self.config.latent_std

        if output_type == "np":
            latents = latents.cpu().numpy()

        if not return_dict:
            return (latents,)

        return WuerstchenPriorPipelineOutput(latents)
